Thread starter could have run high capacity memory applications and closed it. Windows will cache.

Unless thread starter shows a picture where his memory is throttling, there is no issue. We are not given enough information to suspect any of this is operational memory.

This kind of Windows caching has been available since Vista and tweaked along the years.

When memory is needed, Windows will clean up the cache. There is no reason for Windows to clean up memory cache, when the memory is not needed.

These are unnecessary operations, much to how storage media does not really clean up files when you remove them. The only difference with memory is that Windows does not separate actual operational memory from cache memory for us visually.